Method for forming a dry glass-based frit

ABSTRACT

A dry glass-based fit, and methods of making a dry glass fit are disclosed. In one embodiment a dry glass frit comprises vanadium, phosphorous and a metal halide. The halide may be, for example, fluorine or chlorine. In another embodiment, a method of producing a dry glass frit comprises calcining a batch material for the frit, then melting the batch material in an inert atmosphere, such as a nitrogen atmosphere. In still another embodiment, a method of producing a dry glass frit comprises calcining a batch material for the frit, then melting the batch material in an air atmosphere, such as a nitrogen atmosphere

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority under 35 U.S.C. § 119(e) of U.S. Provisional Application Ser. No. 61/106,730 filed on Oct. 20, 2008 the content of which is relied upon and incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention relates to a method for forming a dry frit based on an inorganic glass. More particularly, the present invention relates to a method for forming a dry inorganic glass-based frit suitable for use as a sealing medium for glass packages.

BACKGROUND

Electroluminescent (EL) devices, such as organic light emitting diode devices, are typically manufactured by forming multiple devices in a single assembly using large master (mother) sheets of glass. That is, the devices are encapsulated between two large glass sheets or plates to form a composite assembly, after which individual devices are cut from the composite assembly. Each device of the composite assembly includes a seal surrounding the organic light emitting diodes of the individual device that seals the top and bottom plates together, and protects the organic light emitting diodes disposed within, since some devices, particularly organic light emitting diodes, degrade in the presence of oxygen and moisture that can be found in the ambient atmosphere. The EL devices may be sealed using an adhesive, e.g. epoxy, or more recently, using a glass frit that is heated to melt the frit and form the seal between the two plates.

Frit sealed devices exhibit certain advantages over adhesive-sealed devices, not least of which is the superior hermeticity without the need for getters sealed within the device to scavenge contaminants. Thus, frit sealed devices are able to provide for a longer lived device than has been achievable with adhesive seals. Nevertheless, it has been found that frit sealed devices may succumb to deterioration due to moisture contained in and released by the frit into the cavity housing the organic light emitting material during the sealing process.

SUMMARY

Methods are disclosed for forming a dry glass-based frit suitable for sealing electronic devices, and in particular electronic devices comprising organic materials, such as organic light emitting diode displays, organic light emitting diode lighting panels, and certain classes of organic-based photovoltaic devices.

In one embodiment, a method of forming a dry glass frit is disclosed comprising forming a batch material comprising vanadium and phosphorous, heating the batch material in a conditioning step to a temperature of between about 450° C. and 550° C. for at least about 1 hour, melting the batch material after the conditioning step to form a glass melt, cooling the glass melt to form a glass wherein an OH content of the glass is equal to or less than about 20 ppm as measured by direct insertion probe mass spectrometry.

In another embodiment a glass powder for forming a glass-based frit is disclosed wherein the glass powder comprises vanadium, phosphorous and a metal halide.

In still another embodiment, a glass powder for forming a glass-based frit is disclosed wherein the glass powder comprises V₂O₅, P₂O₅ and a metal halide.

In yet another embodiment, a method of forming a glass frit is disclosed comprising forming a batch material comprising V₂O₅, P₂O₅ and a metal halide heating the batch material in a conditioning step to a temperature of between about 450° C. and 550° C. for at least about 1 hour, melting the batch material after the conditioning step to form a glass melt, cooling the glass melt to form a glass and wherein an OH content of the glass is equal to or less than about 20 ppm.

The invention will be understood more easily and other objects, characteristics, details and advantages thereof will become more clearly apparent in the course of the following explanatory description, which is given, without in any way implying a limitation, with reference to the attached Figures. It is intended that all such additional systems, methods features and advantages be included within this description, be within the scope of the present invention, and be protected by the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of an exemplary glass package comprising an organic material.

FIG. 2 is plot of percent transmittance as a function of wavenumber illustrating a typical measurement for β-OH.

FIG. 3 is a schematic diagram of a DIP-MS apparatus for measuring outgassed water vapor.

FIG. 4 is a graphical representation of a Standard heating schedule according to embodiments of the present invention.

FIG. 5 is a graphical representation of a compressed heating schedule according to embodiments of the present invention

FIG. 6 is a plot showing the results of a DIP-MS measurement conducted on a coarse hand-ground sample of frit composition C₁, showing the extracted ion chromatogram for water.

FIG. 7 is a plot showing the results of a control DIP-MS measurement as conducted in FIG. 6, but without a sample, indicating that the events (spikes) shown in FIG. 6 are related to outgassing of structural water species during the 400-700° C. temperature ramp.

FIG. 8 is a plot showing the results of a DIP-MS measurement conducted on coarse hand-ground samples of control (non-dry) frit composition C₁, showing outgassing of structural water species during the 400-700° C. temperature ramp compared to results for sample C₂ showing no peaks.

FIG. 9 is a photograph that shows fused quartz crucibles of the control batch composition following 485° calcination (left) and 600° C. calcination (right).

DETAILED DESCRIPTION

In the following detailed description, for purposes of explanation and not limitation, example embodiments disclosing specific details are set forth to provide a thorough understanding of the present invention. However, it will be apparent to one having ordinary skill in the art, having had the benefit of the present disclosure, that the present invention may be practiced in other embodiments that depart from the specific details disclosed herein. Moreover, descriptions of well-known devices, methods and materials may be omitted so as not to obscure the description of the present invention. Finally, wherever applicable, like reference numerals refer to like elements.

Hermetically sealed glass packages may be used for a variety of uses, including such photonic devices as optical displays (e.g. flat panel television, cell phones displays, camera displays) and photovoltaic devices (e.g. solar cells). While epoxy seals have been used extensively for certain components, such as liquid crystal displays (LCDs), more recent work is being done on encapsulated organic materials that may be used for similar purposes. For example, organic light emitting diodes are finding application in both display devices and lighting. Certain organic materials are also finding use in the field of photovoltaics, wherein organic solar cells are showing promise.

While organic materials provide some benefit, the organic materials comprising the devices are susceptible to high temperature, oxygen and moisture exposure. That is, when exposed to temperatures in excess of about 100° C., or oxygen or water, the organic material can quickly degrade. For this reason, great care must be taken to ensure devices employing organic materials are hermetically sealed. One such method includes sealing the organic material between glass plates. Inorganic glasses are uniquely suited as containers for housing an organic material. They are substantially environmentally stable, and highly impervious to diffusion of moisture and oxygen. However, the resulting package is only as good as the material that forms the seal between the plates.

Prior art devices have often employed epoxy adhesives as a sealing medium between glass plates. The manufacture of LCD displays is one such example. However, the degree of long term hermeticity required by certain organic materials suitable for use in electronic devices such as the previously mentioned displays, lighting panels and photovoltaic devices is better met by a glass seal between the plates. Thus, the use of an inorganic glass-based frit has become the sealing medium of choice for organic electronic devices.

By way of example and not limitation, an exemplary frit sealing method for organic light emitting diode display 10 (FIG. 1) may comprise forming a photonic element 12 on a first (backplane) glass substrate 14. Photonic element 12 typically includes an anode and cathode electrodes (not shown) and one or more layers of the photonic material (e.g. organic light emitting material) positioned between the two electrodes. A frit 16 is positioned between the backplane substrate and a second glass (cover) substrate 18. The frit may, for example, be first dispensed onto the cover substrate. In some embodiments, the frit is first dispensed as a paste onto cover substrate 18, then heated to sinter the frit and adhere it to the cover substrate. The sintering may be performed in an oven. Cover substrate 18 is then positioned in at least partial overlying registration with the backplane substrate, and the frit heated by an irradiation source 20, such as laser 20 that emits laser beam 22 to soften the frit and form a hermetic seal between the cover substrate and the backplane substrate, thereby producing a hermetic glass package containing the OLED.

In general, water present in glasses can be grouped into two broad categories: structural water where the water atoms (generally present as hydroxyl or OH ions) attach to the glass-forming polyhedra molecular structure during the melting process and become a basic part of the glass network; and surface water where, for example, water molecules present during ball-milling of a glass to produce a frit attach themselves during the milling to unsatisfied valence sites on the frit particle's surface created by broken bonds. Typically, surface water can be removed by a simple drying process, such as by heating the glass of the frit, whereas structural water is much more tenaciously bound, and can persist in the glass during any drying step.

Although the presence of water in a glass does not necessarily degrade glass properties (save for increased mid-IR absorbance), its release (outgassing) during subsequent heating in a frit sealing process may have implications for commercial use of the glass. One particular application affected by water outgassing involves the use of glass frits for sealing OLED devices, which are extremely susceptible to even ppm levels of water. Water, as used herein, may take the form of a vapor phase (such as during outgassing, or as a hydroxyl ion, OH).

In a typical frit manufacturing process, a glass is formed by conventional glass forming methods e.g. sol-gel or by heating granular batch materials (sands). The resulting glass can then be melted, made into thin ribbon, and then ball-milled to a desired particle size. For example, a mean particle size of 3 μm is suitable for use in the manufacture of OLED devices. Following ball-milling, the powdered frit glass may be blended with a filler to obtain a predetermined coefficient of thermal expansion of the frit blend. For example, a suitable coefficient of thermal expansion filler is beta eucryptite. Once the blend has been made and predried, such as heating the blend in an oven, a paste is prepared by mixing the frit glass (or blended frit as the case may be) with an organic vehicle (e.g. texanol), an organic binder (e.g. ethylcellulose), and various dispersants and surfactants as needed. The frit paste is then dispensed into a specific pattern (for example a loop or frame-like pattern) on a glass substrate, heated in air to burn-out the organics, and thereafter exposed to a subsequent heating to 400° C. in N₂ to presenter the frit. As the term implies, the step of presintering consolidates the frit and adheres the frit to the (cover) substrate. Laser-sealing the pre-sintered substrate to a mating substrate (backplane substrate) of one or more OLED devices is typically accomplished using a laser that traverses the consolidated frit, heats and softens the frit and whereupon a seal is formed between the cover substrate and the backplane substrate when the frit cools and solidifies. During laser sealing the frit seal is heated above 400° C. for at least a few tenths of a second, causing structural water (i.e. OH) in the frit to be released, and possibly degrading the OLED.

The effort to eliminate water outgassing in the glass during subsequent heating of the frit to 700° C. has focused on reducing the OH content of the glass. Two approaches were utilized: (1.) composition changes to the glass, and (2.) physical changes to the melting process. Measuring the amount of water was accomplished according to two methods: measuring β-OH (essentially measuring the mid-IR absorbance peak of the OH⁻ ion), and DIP-MS (direct insertion probe mass spectrometry). In accordance with the present invention, a dry glass (and resulting dry frit) is defined as possessing a β-OH value equal to or less than about 0.3 mm⁻¹, or alternatively an OH content equal to or less than about 20 ppm when measured by direct insertion probe mass spectrometry. Preferable, the glass comprises a β-OH value equal to or less than about 0.3 mm⁻¹ and an OH content equal to or less than about 20 ppm when measured by direct insertion probe mass spectrometry. Preferably the glass exhibits no water detectable out-gassing by DIP-MS when reheated to 700° C. either as a coarse hand-ground powder, or as a fine (3 μm) ball-milled powder.

The β-OH measurements were made on annealed pieces of glass that had been ground and then polished to a thickness of 0.1-0.4 mm. β-OH measurements provide data on the total concentration of hydroxyl ions in the glass, not just on those hydroxyls that will de-absorb over a specific temperature region. As shown in FIG. 2 and equation 1 below, β-OH is a ratio of baseline transmittance to transmittance at the OH⁻ absorption peak, and is directly proportional to hydroxyl ion concentration for glasses identical, or very similar, to each other in composition.

β-OH=log(ref % T/OH % T)/(thk)   1

where ref % T is the transmittance level at a nearby non-OH absorbing region, OH % T is the transmittance level at the base of the OH peak (˜3380 cm−1) and thk is the sample thickness (mm).

β-OH is directly proportional to the hydroxyl ion concentration for glasses identical, or very similar, to each other in composition. β-OH measurements provide the relative hydroxyl (OH) absorption coefficient for all hydroxyl ions in the glass, not just on those hydroxyls which will de-absorb over a specific temperature region. Any conventional infrared spectroscopy technique can be utilized for the measurements, such as Fourier transform infrared spectroscopy.

DIP-MS measurements were made on either coarse hand ground (−200M/+100M, or approximately 75-150 μm), or fine ball-milled (equal to or less than an average particle size of 3 μm) powder. Unlike the vacuum furnace mass spectroscopy technique used for many standard mass spec studies, the DIP-MS arrangement, shown diagrammatically in FIG. 3, makes use of a heated probe 28 containing the sample to be tested 30 that is placed directly within the ionization region (electron impact ionizer 32 ) of the mass spectrometer 34. In addition to the above components, the exemplary DIP-MS arrangement if FIG. 3 further includes quadrapole ion analyzer 36 and detector 38. Wavy line 40 represents an ion path from sample 30 to detector 38. Unlike a vacuum furnace mass spectrometry measurement, there is no need for a quartz transfer tube and associated problems of deposition of chemical species, or permeability of the tube at high temperatures. Thus, the DIP-MS measurement lends itself to more reliable quantitative analysis of chemical species.

Two different heating schedules were used for the DIP-MS measurements: a) a Standard Cycle (FIG. 4) where the sample was heated to 400° C., held for 5 hrs to remove any surface water, and then heated to 700° C. at a rate of 10° C./min., and b) a Compressed Schedule (FIG. 5) which utilizes the same temperature ramp-up to 400° C. as the Standard Schedule, but includes a shorter hold time at 400° C. (2 hrs), and utilizes a faster heat-up ramp to 700° C. (50° C./min.). All samples were heated in vacuum throughout the entire DIP-MS run.

Shown in FIG. 6 are the results of a DIP-MS measurement conducted on a coarse hand-ground sample of a frit glass composition suitable for laser sealing of an OLED device showing the extracted ion chromatogram for water (and plotted a nano-Amperes as a function of. time in minutes). The run was made on the Standard Schedule. A small amount of water outgassing from surface water was recorded in the first few minutes of the run as the sample was heated to 400° C. During the 4 hr hold at 400° C. (from 20 min to 260 min), no additional water out-gassing events were recorded, confirming that the initial water evolution was related to surface water. Once sample heating resumed, several discrete events related to water evolution are observed beginning at approximately 550° C.

Note that these discrete events are not observed when a control measurement is run without a sample (FIG. 7), further indicating that the events are related to outgassing of structural water species during the 400-700° C. temperature excursion. Only a broad undefined shallow peak is observed as a characteristic of the general background signal of the instrument during the control measurement.

As noted in Table I, the use of halide compounds was found to be particularly effective for reducing structural water levels, as indicated by both the significantly-lowered β-OH levels of the halide-containing compositions, as well as by the complete absence of detectable water outgassing during the 400-700° heating ramp as detected by the DIP-MS measurement. Table I provides a summary of the results for 4 compositions (C₂-C₄) compared to a control composition (C₁) without a halide. Shown in FIG. 8 is a comparison of the high temperature portion of a DIP-MS scan for the non-halide containing C₁ sample, and the substantially identical C₂ sample with all Al₂O₃ replaced by AlF₃. Both materials were coarse, hand-ground glass powders. The scan for the fluorine-containing glass (C₂) represented by curve 42 shows a featureless pattern with no distinct events. By contrast, the scan for the C₁ sample represented by curve 44 shows several discrete water evolution events occurring in the approximately 550-650° C. range. The β-OH value for the C5 sample was higher that expected, and out of line with the other halide results, and is believed to be a result of poor sample preparation (as the β-OH measurement is sensitive to surface cleanliness of the sample). DIP-MS measurements for sample C3 and C4 were not conducted.

TABLE I C₂ C₃ C₄ C₅ (all (50% of (25% of (67% of C₁ Al₂O₃ Al₂O₃ Al₂O₃ Al₂O₃ (standard added added as added as added as (mole %) composition) as AlF₃) AlF₃) AlF₃) AlCl₃) Sb₂O₃ 22.9 22.9 22.9 22.9 22.9 V₂O₅ 46.3 46.3 46.3 46.3 46.3 P₂O₅ 26.3 26.3 26.3 26.3 26.3 Fe2O3 2.4 2.4 2.4 2.4 2.4 Al2O3 1.0 1.0 1.0 1.0 1.0 TiO2 1.0 1.0 1.0 1.0 1.0 F⁻ — 6.0 3.0 1.5 — (added) Cl⁻ — — — — 2.0 (added) β-OH 0.42-0.43 0.15 0.18 0.23 0.548 (2 melts) H₂O 175, 224, 251 None None evolved, (3 different detected detected DIP-MS, powder lots) ppm

In addition to the including halides in the frit, additional trials were conducted independently of halide incorporation where the melting process was modified to produce glasses with low β-OH values and which did not exhibit structural water outgassing during subsequent DIP-MS analysis.

Shown in Table II is a listing of the various process change experiments and the structural water level measured (β-OH) and/or the quantity of structural water evolved (DIP-MS). As may be seen, these various experiments involved determining the effect of thermal cycling during melting (Experiment 1), air-calcining of the batch material with N₂ melting (Experiment 2), air-calcining of the batch material (either 485° or 600° C.) combined followed by air-melting (Experiments 3 and 4) of the batch material; melting all but the V₂O₅ component of the basic glass, then re-melting with V₂O₅ (Experiment 5); and re-melting standard cullet in an induction furnace and bubbling O₂ or N₂/O₂ through the melt during re-melting (Experiments 6 and 7). Most of these approaches resulted in a substantially lower β-OH value and/or no structural water outgassing detected by DIP-MS measurement relative to the standard process, with the exception of high-to-low-to-high thermal cycling during melting (Experiment 1); and 600° calcining plus standard 1000° C. melting (Experiment 5).

TABLE II Experi- DIP-MS ment # Details DSC Water, ppm β-OH control Melt at 1000° for 1 hr in 355° 175, 224, 251 0.471 air 1 Melt at 1000° for 1 hr, 354° 925 0.336 lower temp to 600°, hold 2 hrs, re-melt at 1000° for 1 hr (in air) 2 Calcine in air at 485°, 359° not detected 0.137 melt in N₂ at 1000° 3 Calcine in air at 485°, 356° not detected 0.205 melt in air at 1000° 4 Melt Sb₂O₃—P₂O₅ glass not detected (using ammonium phosphate), grind, mix with V₂O₅ and re-melt at 1000° in air to yield a 25:25:50 Sb₂O₃—P₂O₅—V₂O₅ glass 895BHL 5 Calcine in air at 600°, 0.433 melt in air at 1000° 6 Induction melt 895ASF 220°, not detected cullet at 900° in N₂, and 362° bubble O₂ 7 Induction melt 895ASF 359° not detected cullet at 900°in N₂, and bubble 80% N₂—20% O₂

An interesting feature of the results is the effect of calcining temperature. Calcining was selected as a potential means to reduce structural water since it would permit water present as a constituent of any raw materials of the frit blend to escape from the batch before being accommodated into the melt structure. Interestingly, 485° C. air-calcining/1000° C. air-melting (Experiment 3) had a substantial effect in lowering the amount of structural water (β-OH=0.205), but 600° C. air-calcining/1000° C. air-melting (Experiment 5) was relatively ineffective (β-OH=0.433). A possible explanation is provided by FIG. 9, which shows fused quartz crucibles 46 and 48 of the control batch composition following 485° calcination and 600° C. calcination, respectively. The calcined 485° C. batch is essentially a loose, porous, unconsolidated powder, whereas substantial melting occurred with the 600° C. calcined batch, since the melting point of one of the key batch components (phosphorus pentoxide) is 563° C. One possible explanation is that the liquid phase generated at 600° C. sealed off many escape passages for evolved water, leading to greater incorporation of water in the melt structure than with the lower temperature 485° C. calcining. The combination of 485° C. air-calcining 1000° C. with N₂-melting (Experiment 2) produced the lowest β-OH of all approaches. It is believe this occurred because the effect of 485° C. air-calcining was combined with the ability of N₂ to sweep through the glass melt and carry off water species. The beneficial effect of N₂ was also observed for Experiments 6 and 7, where conventionally-melted cullet was re-melted in a N₂ atmosphere with either O₂ or N₂/O₂ bubbled through the melt.

Following the completion of the physical experiments in Table II, three approaches were selected for repeat testing to determine reproducibility of the water-free results. These were: halide replacement of Al₂O₃ (e.g. AlF₃); 485° C. calcining in air for 2 hr. followed by melting at 1000° in air; and 485° C. calcining in air for 2hr followed by melting at 1000° in a N₂ atmosphere. A comparison of these techniques are shown in Table III with respect to β-OH and water outgassing results. The three approaches which produced a dry glass in the initial experiments produced dry glass in the repeat work.

TABLE III 485° C.- 485° C.- 2 hr air + 2 hr air + 1000° C.- 1000° C.- C₁ C₂ 1 hr (N₂) 1 hr (air) DIP-MS H₂O 175, 224, 251 Not Not Not (ppm) all samples (Av, 217 ppm) detected detected detected coarse-ground β-OH (abs/mm) 0.38-0.61 0.07-0.11 0.02-0.16 0.19-0.24 range all samples polished bulk

The absence of structural water out-gassing seen above for several of the approaches was also seen in a fine-ground (equal to an less than about 3 μm particle size) ball-milled powder, as well as for frit blend pastes made of the fine-ground powders after a 400° C. presintering treatment as indicated by the DIP-MS results provided in IV.

TABLE IV DIP-MS Results (high temperature regime, 400-700° C.) 2% AIF₃ replacement 485° C.-2 hr for 1% Al₂O₃ air calcine + (standard 1000° C.- 1000° C.- 1 hr air melting) 1 hr N2 melting Coarse-ground powder Not detected Not detected (75-150 μm) Fine-balled milled Not detected Not detected powder (<3 μm) Presintered frit paste made Not detected Not detected from fine ball-milled powder and low CTE filler (70:30 blend)

The several techniques described above for producing dry glass and frits appear to have relevance to vanadium and phosphate containing glasses in general, rather than to just the Sb₂O₃ vanadium phosphate glasses currently used for OLED frit sealing. Shown below in Table V are β-OH values for an Sb-free, Fe₂O₃—V₂O₅—P₂O₅ glass according to an embodiment of the present invention.

TABLE V C₆ Fe₂O₃ 17.5 TiO₂ 17.5 ZnO 5.0 Composition P₂O₅ 20.0 (mole %) V₂O₅ 40.0 β-OH (abs/mm) 0.49 standard melting (1000° C.-1 hr, air) β-OH (abs/mm) 0.03 calcine + N₂ melting (485° C.-2 hr, air + 1000° C.-1 hr, N₂)

It should be emphasized that the above-described embodiments of the present invention, particularly any “preferred” embodiments, are merely possible examples of implementations, merely set forth for a clear understanding of the principles of the invention. Many variations and modifications may be made to the above-described embodiments of the invention without departing substantially from the spirit and principles of the invention. All such modifications and variations are intended to be included herein within the scope of this disclosure and the present invention and protected by the following claims. 

1. A method of forming a glass frit comprising: forming a batch material comprising vanadium and phosphorous; heating the batch material in a conditioning step to a temperature of between about 450° C. and 550° C. for at least about 1 hour; melting the batch material after the conditioning step to form a glass melt; cooling the glass melt to form a glass; and wherein an outgassed water content of the glass is equal to or less than about 20 ppm.
 2. The method according to claim 1, further comprising grinding the glass to form a glass particulate.
 3. The method according to claim 1, wherein the glass comprises a O-OH equal to or less than about 0.3 mm⁻¹.
 4. The method according to claim 2, further comprising blending the glass particulate with a coefficient of thermal expansion lowering filler material.
 5. The method according to claim 1, wherein the batch material is heated in the conditioning step for a period of at least about 2 hours.
 6. The method according to claim 1, wherein the vanadium is V₂O₅.
 7. The method according to claim 1, wherein the phosphorous is P₂O₅.
 8. The method according to claim 1, wherein the glass is free of antimony
 9. The method according to claim 1, wherein the melting is performed in air.
 10. The method according to claim 1, wherein the melting is performed in a nitrogen atmosphere.
 11. The method according to claim 1, wherein the melting comprises heating the batch material to a temperature of at least about 1000° C. to melt the batch material.
 12. A glass powder for forming a glass-based frit, wherein the glass powder comprises vanadium, phosphorous and a metal halide.
 13. The glass powder according to claim 12, wherein the glass powder is free of antimony.
 14. A glass powder for forming a glass-based frit comprising V₂O₅, P₂O₅ and a metal halide.
 15. The glass powder according to claim 14, wherein the metal halide comprises AlF₃.
 16. The glass powder according to claim 14, wherein the glass powder comprises AlCl₃.
 17. The glass powder according to claim 14, wherein the metal halide is selected from a halide of a metal selected from the group consisting of iron, vanadium and aluminum.
 18. The glass powder according to claim 14, wherein the glass powder is free of antimony.
 19. A method of forming a glass frit comprising: forming a batch material comprising V₂O₅, P₂O₅ and a metal halide; heating the batch material in a conditioning step to a temperature of between about 450° C. and 550° C. for at least about 1 hour; melting the batch material after the conditioning step to form a glass melt; cooling the glass melt to form a glass; and wherein an OH content of the glass is equal to or less than about 20 ppm.
 20. The method according to claim 19, wherein the batch material comprises antimony.
 21. The method according to claim 19, wherein the glass comprises a β-OH equal to or less than about 0.3
 22. The method according to claim 19, wherein the batch material is heated in the conditioning step for a period of at least about 2 hours
 23. The method according to claim 19, wherein the melting is performed in air.
 24. The method according to claim 19, wherein the melting is performed in a nitrogen atmosphere. 